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nitrogen from the bloodstream. Such waste builds up every time we eat protein; if it doesn’t get cleared, it causes nerve damage.

Johns Hopkins researcher Saul Brusilow did pioneering work that led to the development of the first treatment for patients with this disorder, a drug called sodium phenylbutyrate (Buphenyl). The treatment, Nash says, “has been a true lifesaver,” for patients with urea cycle disorders.

But you knew there would be a catch, right? Adults on the existing drug have to take about 40 vitamin-size pills per day, and the drug tastes and smells bad. The dose is tailored based on weight, so children don’t have to take quite as much, but parents often find it hard to get their kids to take the medicine, Nash says.

So Hyperion’s goal is to see if it can do better with a lower dose formulation, taken in three teaspoons per day, that has no taste or smell, Nash says.

The trial whose results Hyperion unveiled yesterday was conducted with a special protocol assessment with the FDA, essentially a written agreement that said this single study, should it prove successful, ought to provide a sufficient for market approval of the drug, Nash says. The goal was to show that the new drug was considered “non-inferior” to the existing product.

The main measurement of effectiveness was how much ammonia was found in patients’ blood at days 14 and 28 of treatment. At the end, researchers found that patients on the new drug had, on average, 34.7 micromoles per liter of ammonia in their blood, while those on the older treatment had a higher level, 38.4 micromoles per liter. The result is noteworthy because doctors consider 35 micromoles per liter to be the “upper end of normal” for ammonia concentration in the blood, Nash says.

The most common side effects reported in the study were diarrhea, flatulence, headache, vomiting, fatigue, lack of appetite, and stomach pain, Hyperion said. More detailed results are expected to be presented at the American College of Medical Genetics meeting, or the Society of Inherited Metabolic Disorders conference, before the end of March, Nash says. Findings will also be published in a peer-reviewed scientific journal, she says.

The regulatory pathway for Hyperion’s drug should be pretty straightforward, as Nash assured me the company has had no indication that the FDA will require more clinical trials—as it often does with drugs for common conditions such as diabetes or obesity. If talks go well with the FDA, and the agency clears the product for sale, Hyperion will move ahead with plans to market the drug itself to this small, manageable population of patients and doctors.

“We are familiar through the clinical trials with many of the key physicians,” Nash says. “And as we’ve seen in other small markets, when new treatments come along, there’s often new interest and increasing diagnosis of these patients.”